provide post-build hook capability prior to creating .tar.gz #11

There are several cases I can imagine for this. In my case, I have a very common one.

We have the well-known issue where the bundled urllib leverages the bundled openssl which comes with no certificate file, and thus cannot verify any certificates out of the box.

With a post-build hook, we could export a cacert.pem file from the system or from another location and bundle it with the .tar.gz. That would also require us patching some source somewhere to instruct the bundled openssl to use it. There are a few options for that part.

Obviously, we can un-tar, modify, and re-tar, but I don't want to do that.

Another common case I can imagine would be to do pip install of some extra packages prior to bundling (I'm not sure if that can actually work or not, but I believe so.).

Alternatively, if you'd prefer to provide some first-class mechanism for solving the "lack of a bundled cacert" problem, that would help us with the immediate issue so that would be great as well.

Anyway, feedback welcome.